1. Field
The present invention relates generally to a tube seal system used to protect communications in subsea environment, and more particularly, to a tube seal system which can provide a high reliability and redundant penetrations through pressure boundaries.
2. Related Art
In communications, it is common practice to package copper and fiber optic conductors in stainless steel tubes (SSTs) that are part of a cable, and to create pressure-tight tube seals to allow the tubes carrying copper and fiber optic conductors to penetrate into pressure housings. Many methods have been employed solve this technical problem of providing a pressure-tight tube seals into pressure housings in a subsea or other high pressure gradient environment.
Here are some of related art tube seals used in the field.
1. Elastomeric interference seals: These seals are common in subsea pressure housing tube penetration applications and provide a radial seal on the tube.
2. Swages: Swaging involves loosely fitting parts together, and compressing and deforming the fitting ferrule and tube interface using a mechanical or hydraulic tool, creating a permanent joint. These seals are common in a wide variety of pressure sealing applications, such as, instrumentation, subsea pressure housing tube seals, chemical processing pressure seals, mining, and nuclear.
3. Epoxy Cones: These seals are common in subsea pressure housing tube penetration applications.
4. Gland Seals: These seals function by axial compression and are common in subsea pressure housing tube penetration applications.
5. Ferrule-based penetrators: These seals involve having two optical-ferrules making contacts across a pressure boundary.
However, here are some of the challenges faced by current tube sealing technology used in subsea systems. First, by using swages without Elastomeric interference seal, these seals are susceptible to over-tightening at installation and prone to mechanical creep failure. Second, using Elastomeric interference seals without redundant swage may cause elastomeric material failure if the seal is directly exposed to chemicals.
On the other hand, gland seals are effective in low pressure applications only, and if the gland seals are exposed directly to environment, they could be degraded by trace chemicals or UV-exposure.
O-rings can point load and crush/deform a tube at high pressures resulting in seal leakage or tube failure.
In using epoxy glands penetrations, there exists the potential for possible bond-line delamination between the tube-epoxy interface resulting in leakage.
Lastly, ferrule-based penetrators can be expensive, bulky, and susceptible to contamination during assembly. Further, contact between ferrules in high pressure applications may result in high optical loss.
These methods typically provide a single leak path protection which may limit long-term seal reliability and deployment depths. The current invention provides a means to provide an all mechanical, redundant tube seal that provides a greater long-term reliability than what is available in current art.